1. Field of the Invention
This invention relates to polyimides and the monomers used in their formation. More particularly, it relates to monomers which impart increased solubility to the polyimides produced therefrom.
2. Description of the Prior Art
A basic problem with many polyimides is their low solubility in most solvents. This limitation prevents their use in many coating applications where it is necessary to dissolve the polymer in a solvent in order to apply it to the surface to be coated. In addition, these polymers are generally high melting, intractible solids which are difficult to mold or process.
U.S. Pat. No. 3,450,678 describes a number of polyimides, including those derived from 4-aminophthalic anhydride, which also suffer from the aforementioned problems. However, it has been discovered that these detrimental properties can be overcome by incorporating a t-butyl group onto the aromatic ring of the monomer. It is believed that the presence of the t-butyl group lowers the crystallinity of the polyimide and correspondingly imparts better solubility and moldability. These new monomers, most specifically including 4-amino-5-t-butylphthalic anhydride, monomethyl 3-amino-5-t-butylphthalate, and dimethyl 4-amino-5-t-butylphthalate, can be polymerized in various proportions to produce improved homopolymers and copolymers with a range of improved properties, depending upon the amount of the monomer incorporated into the polyimide.
Accordingly, it is an object of this invention to produce new monomers which impart improved solubility to the corresponding polyimide.
It is a further object of this invention to produce new polyimides.
These and other objects will become clear upon further reading of the specification.